Developing+Parametric+Families+in+Revit

The most important part of creating a family is to have a clear idea of what you want to create before you start modeling.

Opening the Template
To start the new familly, open the pulldown menu File>New>Family as shown in Figure 1. The next step is to determine the type of family to create. There are many options available, but one will suit the goal best. If creating ceiling based objects, it is better to open the ceiling template. If creating a lighting fixture, it is best to use the lighting fixture template. Review the potential families and match the family template with the closest function.

For this lesson, we will use the generic model because we are making a simple parametric cube. Once it has opened, you will see a screen similar to Figure 2.

[[image:Figure_2.jpg caption="Figure 2"]]Tiling the Windows
The best way to create a model is to continually view it in all dimensions. To do this tile the screen. Go to the Window pulldown and select tile, (see figure 3). This will resize and relocate all of the open windows.



Reference Planes
Now that all of the setup is complete, it is time to start the family. To begin, make a parametric cube. This may seem simple, but the basis for parametric families is very important. The first step is to create a reference plane for each boundary of the cube. A reference plane is an infinite surface that Revit uses to control dimensions of an object. In the view entitled "Family1-Floor Plan: Refl Level" (located at the top of each viewing window) we will insert four reference planes. To do this, click on Ref Plane in the Design toolbar, as shown in figure 4, to the left of the screen. Create a square around the intersecting lines in the middle (see figure 5).

In the view entitled "Family1-Elevation: Front" insert a reference plane intersecting the two planes perpindicular to the view just added (see figure 6). The next step is to add dimensions.



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Dimensioning


Dimensioning allows the use of parametric settings within Revit. Click on Dimension in the design tool bar, and then click on the two horizontal lines in the front elevation view (see figure 7). After this is done, click on the dimension. The tool bar above the views will appear with more options. Click the down arrow beside Label and select "Add Parameter".

In the window that pops up, type in "Height of Cube" under name. In the drop down menu entitled "Group Parameter Under" select Dimensions (see figure 8).

There are two radio selectors that you can choose from below the drop down menu. You can either choose Instance or Type. An Instance parameter is one which can individually be changed, where as the Type parameter changes every one of the objects to that setting once inserted. This is an important difference. If the purpose is to create one type of chair in a project and they all must be the same, then the Type parameter is the best choice. If the purpose is to create a window that can be multiple sizes within the same project, than Instance is the better choice. For this we will leave it set to Type.

Repeat the same process in the Ref. Level view for the two other directions and name them Length and Width. This time however, select the Instance radio button for both instead of Type. When finished, the view will look like the one in figure 9.

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Massing
The next step in the process is creating the mass. For this, an extrusion will be used. To start the extrusion, activate the Ref. Level view by clicking anywhere in the window. Next, go to the design toolbar and click Solid Form>Solid Extrusion (see figure 10).

Trace a square over top of the outside reference planes. Make sure they are right above the dashed green lines. By doing this, the extrusion boundaries are beeing locked to the reference planes. This is a key part to parametric functionality. By locking them together, if the reference plane dimension changes, so does the extrusion. When you are finished drawing the lines, the square will look like the one in figure 11.



Extrusion Properties
Once the square is completed, click on "Extrusion Properties" in the design toolbar. An element properites window will appear. Under Constraints, the first listed item is "Extrusion End". To the far right of this you will see a little gray box (highlighted in figure 12). This is a button that can be clicked to assign a parameter. Click the button and an Associate Family Parameter window will appear.

When the window appears, you will notice all of the parameters previously created as in figure 12. For this, the "Height of Cube" parameter will be assigned. Click on it, then click okay. You will notice that the ability to type any value into the Extrusion End spot is lost. The new value is that of the actual distance between the reference planes. Before closing the Element Properties window, click on the "Materials and Finishes" parameter setting box. Another Parameter Properties window will appear again as in figure 13, but this time there are no parameters to choose from. Click on "Add Parameter." Name the parameter, "Cube Material", then from the drop down list select "Materials and Finishes". Select the Instance Radio button, and then select okay. Go ahead and click okay once again and the extrusion height and materials are now set

To end this extrusion, select "Finish Sketch." There should now be a cube in the 3D View. It should look something like the one in figure 14. Return to Top of Page

Saving the File
The next thing to do is save the file. Go to the pulldown menu File>Save As and save the file to a folder location where you will save your newly developed families. Give it a name like "Cube" (see figure 15). After saving the file, go to File>Close. This will close all of the windows.

Loading the new Component
Open a new project, like any other normal project. Click Component from the design toolbar then click Load. Go to the directory where you saved the file and load the component. Place the component anywere into the project. Select the cube on the screen and go to the element properties button. An element properties window will appear. As you can see there are options under "Materials and Finishes" and "Dimensions" which you can change as in figure 16. Select a new material and change some of the dimensions. After doing this, click on "Edit/New" from the top of the window. This will allow you to change the height of the cube. Remember, if the height of the cube changes, which is a Type Parameter, it will change all of that family's heights. After doing this, look at the cube in a 3D View. In order to view the color of the material selected, use the Shortcut Keys in Revit. To shade the view quickly type SD or go to the drop down menu View>Shaded View. It may or may not resemble the one in figure 17 depending on the selected materials or dimensions.

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